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Redundant usage of unmodifiable collection wrappers

Reports redundant calls to unmodifiable collection wrappers from the Collections class.

If the argument that is passed to an unmodifiable collection wrapper is already immutable, such a wrapping becomes redundant.

Example:

List<String> x = Collections.unmodifiableList(Collections.singletonList("abc"));

After the quick-fix is applied:

List<String> x = Collections.singletonList("abc");

In order to detect the methods that return unmodifiable collections, the inspection uses the org.jetbrains.annotations.Unmodifiable and org.jetbrains.annotations.UnmodifiableView annotations. Use them to extend the inspection to your own unmodifiable collection wrappers.

New in 2020.3

Inspection Details

By default bundled with:

IntelliJ IDEA 2024.1, Qodana for JVM 2024.1,

Can be installed with plugin:

Java, 241.16690

Last modified: 29 April 2024